I'm currently having trouble to perform importance sampling with CosmoMC. I want to add the constraints from the JLA supernovae data to chains that were run only with planck data. So I took my .ini file and changed this :

I managed to understand that this comes from the fact that we need 2 nuisance parameters to run with the JLA sample that are absent when using only planck data : alpha_jla and beta_jla.
So I have two questions :
- how can I do what I'm wanting to do ?
- why does cosmomc stop when the number of parameters with the previous run is not the same as the new one when doing importance sampling since it must be a quite common situation ?

Hi Antony,
Thank you for your quick answer !
Quick question : I don't know much about it so, is it inherent to the technique of importance sampling or is it the implementation that forbids to change the number of parameters ?